Automatic exposure control apparatus and method

ABSTRACT

An automatic exposure (“AE”), control apparatus to prevent exposure errors resulting from “smear.” Image-capturing is performed at a single exposure time TI (I=1, 2, . . . n); a CCD output is applied with a CCD drive signal to perform an integrating operation for a signal in an AE area using an integration circuit, and then outputs integration value EI+SI at each exposure time. A shutter trigger operation presents readout of an exposure value. An integrator value En+Sn obtained just before the shutter trigger operation, and a smear value Sn′ obtained just after the shutter trigger operation are provided to an exposure operation/control circuit. The exposure operation/control circuit then performs an AE operation to receive En+Sn−Sn≈En and compares the value to a target value for determining exposure conditions, and provides an AE operation value containing almost no smear component to determine an appropriate exposure condition.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.09/165,414, filed Oct. 2, 1998, now U.S. Pat. No. 6,618,090 which ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to an automatic exposure control apparatusthat automatically controls exposure by utilizing an output signal of asolid-state imaging device.

2. Description of the Related Art

Recently, there has been increasing use of electronic image-captureapparatuses that use an imager, which employs a solid-state imagingdevice to capture subject images, and that record the captured images ina storage medium of semiconductor memory or magnetic tape.

To automatically set an image-capture optical system in an image-captureapparatus such as that described above under appropriate exposureconditions, an automatic exposure control apparatus is employed.

As a type of automatic exposure control apparatus, there is an apparatusthat makes use of an output from a charge-coupled device (hereinafterreferred to as a “CCD”) to perform automatic exposure control (aso-called “imager AE”); more particularly, there is an apparatus thatintegrates an automatic exposure sensing area of an image output from aCCD and refers to the integration result to determine exposureconditions (such as shutter speed and diaphragm aperture adjustment).

FIG. 5 is a timing chart illustrating an example of an automaticexposure control operation of a conventional automatic exposure controlapparatus. In this figure, each of the horizontal axes represents timeand is separated into two sections because of limited space, the rightend of the axis in the upper section continuing to the left end of theaxis that has the same alphabetical letter (i) (i=a, b, . . . , f) inthe respective lower section. Other figures such as FIG. 2 are displayedin the same way.

In FIGS. 5,(a)–(f) respectively represent a mecha-shutter, CCD readoutpulse ON/OFF (ON permits a readout-pulse output; OFF inhibits areadout-pulse output), exposure time, CCD output, AE area integration,and AE operation.

The mecha-shutter is kept in an OPEN state until it receives a shuttertrigger, but it changes to a CLOSE state upon receipt of a shuttertrigger.

Regarding the CCD readout pulse, it is transferred from a photosensitivearea (photoelectric conversion area) of the CCD, and it is always keptin an ON state.

After an exposure time TI, a signal charge of the CCD photoelectricconversion area is then transferred to a transfer area as a CCD readoutpulse, the transferred signal charge has vertical and horizontaltransfer pulses applied to it, and then it is output from the CCD.

The CCD output signal which corresponds to an AE sensing area issubjected to an integrating operation. This is indicated as theintegration value EI+SI as an AE area integral. Here, EI represents anintegration value of net signal charge accumulated in the CCDphotoelectric conversion area (the AE sensing area of) at the exposureperiod TI; SI represents an integration value of a so-called smearoccurring in a vertical transfer area because of oblique incidencetransmission of a bright subject image and the like.

An operation area for performing an automatic exposure operationperforms an AE operation to compare the integration value EI+SI to atarget value. If EI+SI>target value, the operation area then determinesthe next exposure time TI+1 so as to be TI>TI+1; while, if EI+SI<targetvalue, it then determines the next exposure time TI+1 so as to beTI<TI+1.

In this way, the next exposure time is consecutively determined, and ifa release operation is performed after an exposure time Tn and a shuttertrigger are received, the exposure time required for actualimage-recording is then determined from the integration value En+Sn; andafter the exposure time is determined, it is further transferred as aCCD readout pulse to a transfer area, the mecha-shutter is shut off, andthen a CCD output is produced through application of the vertical andhorizontal transfer signals.

In this state, the mecha-shutter is kept shut; therefore, the smearintegration value is zero (0). This is different from the condition inwhich the AE operation is performed by determining exposure time bykeeping the mecha-shutter open.

Particularly, before performing exposure, the next exposure time haspreviously been determined when there has always been a smear componentpresent existed; however, at the time of actual exposure, the exposureamount is reduced by the amount corresponding to the smear componentwhen it is not present. This indicates that the exposure amount at anactual exposure time is set as En/(En+Sn), which is reduced tocorrespond to the smear component ratio.

For this reason, defects have occurred in that the larger the smeareffect, the darker the captured image has been.

With the conventional example, in a bright scene in which the smearoccurs and at the imager AE, the required exposure time has beendetermined on the basis of CCD output in consideration of smearinclusion, so that when images are captured by use of a camera allowinguse of a mecha-shutter or diaphragm thereof to reduce the aperture,defective captured images being dark in proportion to the smear amountare produced.

SUMMARY OF THE PRESENT INVENTION

In consideration of the aspects described above, the present inventionhas been made to provide an automatic exposure control apparatus whichcan prevent exposure errors resulting from smears when determiningexposure conditions of digital cameras and the like to record images ofbright scenes in which smears occur.

A first automatic exposure control apparatus according to the presentinvention receives an exposure evaluation value from an output signal ofa solid-state imaging device and uses the evaluation value as areference value to perform automatic exposure control for thesolid-state imaging device; in which by receiving an exposure evaluationvalue containing almost no smear component from two output signalsreceived through application of the same drive signal from thesolid-state imaging device that has image-captured in a first exposuretime and in an exposure time which is practically twice that of thefirst exposure time, automatic exposure control with almost nosmear-component effect can be performed. In addition, images can berecorded in an appropriate exposure condition with almost no exposureerror resulting from the smear component even in bright scenes at theactual exposure time.

A second automatic exposure control apparatus according to the presentinvention which receives an exposure evaluation value from an outputsignal of a photoelectric conversion area performing photoelectricconversion and an output signal of a solid-state imaging devicecomprising a transfer area in which the signal is transferred from thephotoelectric conversion area and uses the evaluation value as areference value to perform automatic exposure control for thesolid-state imaging device comprises: a first drive means to transfer asignal in a photoelectric conversion area in each exposure period to atransfer area and then to output the signal from a solid-state imagingdevice; and a second drive means to output a signal in a photoelectricconversion area from a solid-state imaging device, while nottransferring the signal to a transfer area; in which by receiving anexposure evaluation value containing almost no smear component from twooutput signals received from the first drive means and the second drivemeans, it is possible to automatically determine exposure with almostno-smear-component effect even in bright scenes in which smears occur.

A third automatic exposure control apparatus according to the presentinvention which receives an exposure evaluation value from an outputsignal of a photoelectric conversion area performing photoelectricconversion and an output signal of a solid-state imaging devicecomprising a transfer area into which the signal is transferred from thephotoelectric conversion area and uses the evaluation value as areference value to perform automatic exposure control for thesolid-state imaging device comprises: a first drive mode to transfer,before a release operation, a signal in a photoelectric conversion areain each exposure period to a transfer area and then to output the signalfrom a solid-state imaging device; and a second drive mode foroutputting, after a release operation, a signal in a photoelectricconversion area from a solid-state imaging device without transferringthe signal to a transfer area; in which by receiving an exposureevaluation value containing almost no smear component from an outputsignal received in the second drive mode and an output signal receivedin the first drive mode just before the second drive mode signal, anexposure evaluation value containing almost no smear component can bereceived after the release operation; thereby allowing recording ofimage subjects at appropriate exposure with almost no smear-componenteffect even in bright scenes in which smears occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a general construction of a digitalstill camera comprising an automatic exposure control apparatus of afirst embodiment of the present invention.

FIG. 2 is a timing chart for a description of operation of the firstembodiment of the present invention.

FIG. 3 is a timing chart for a description of operation of a secondembodiment of the present invention.

FIG. 4 is a timing chart for a description of operation of a thirdembodiment of the present invention.

FIG. 5 is a timing chart illustrative of operation of a conventionalexample.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to the drawings, embodiments of the present invention aredescribed below.

FIGS. 1 and 2 are relevant to a first embodiment of the presentinvention; FIG. 1 is a block diagram showing a general construction of adigital still camera comprising an automatic exposure control apparatusof a first embodiment of the present invention; and FIG. 2 is a timingchart for a description of operation of the first embodiment of thepresent invention.

As shown in FIG. 1, in a digital still camera 1 for use in the firstembodiment, light from an image subject enters a CCD 5, an imager,through an image-capture lens 2, a mecha-shutter 3, and a diaphragm 4which are set along the optical axis.

In the CCD 5, signal charge accumulated in a photoelectric conversionarea (photosensitive area) formed by a photodiode array for forming aphotoelectric conversion pixel is transferred from the photoelectricconversion area to a vertical transfer area by a CCD readout pulse. Inaddition, through application of a vertical transfer signal and ahorizontal transfer signal, a signal charge in the vertical transferarea is vertically transferred, and concurrently, a sequential signalcharge is output from an output terminal of the horizontal transferarea.

To the CCD 5 is applied a CCD drive signal (such as a CCD readout pulseand a transfer signal composed of a horizontal signal and a verticalsignal) from a timing generator circuit (hereinafter referred to as a“TG circuit”) 6; thereby an image-capture signal (or an image signal) isoutput from the CCD 5, and then the image-capture signal is sample-heldby a sample/hold circuit 7 in the unit of a pixel so that only a signalcomponent is extracted.

Furthermore, the extracted signal component is then gain-conditioned ina gain control circuit (hereinafter referred to as a “GC circuit”) 8 andis input to an A/D converter 9 so as to be converted from the analogsignal to a digital signal. The sample/hold circuit 7 and the A/Dconverter 9 then receive a timing signal from the TG circuit 6 toperform sample-holding and A/D conversion with a predetermined timing.

The digital signal that is output from the A/D converter 9 is then inputto a signal conditioning circuit 10, therein signal-conditioned andconverted to an image signal, and input to a record system 11 comprisinga record medium such as a memory card and to a liquid crystal displaydevice (hereinafter referred to as an “LCD”) 12, which displays images.

The LCD 12 then displays the subject image. At this stage, when arelease switch (not shown) is operated, a shutter trigger which is torecord image subjects is actuated to record the subject image in therecord medium.

The aforementioned digital signal is input to an integration circuit 13that generates a signal of an AE integration value which integrates thedigital signal in an exposure-sensing area to perform automaticexposure. (referred to as “AE”) corresponding to the brightness of theimage of the subject. The generated signal is output to an exposureoperation/control circuit 14. This exposure operation/control circuit 14comprises a function for controlling the aperture (exposure amount) ofthe diaphragm 4, open/close operations of the mecha-shutter 3, andCCD-shuttering by means of the CCD 5, synchronously with the timingsignal from the TG circuit 6, so that the image is recorded in therecord system 11 in an appropriate condition in regard to the brightnessand the exposure amount.

This exposure operation/control circuit 14 also comprises anotherfunction for controlling integrating operations for the gain of the GCcircuit 8 and in integration circuit 13.

This first embodiment is characterized in that the exposureoperation/control circuit 14 performs an ON/OFF control through the TGcircuit 6 so that an AE integration value containing almost no smearcomponent is produced through operations with CCD outputs in ON and OFFstates, whereby an image is recorded in exposure conditions with nosmear effect in actual exposure and image-recording.

In particular, in a first drive period a common CCD drive method is usedto expose the photoelectric conversion area, to transfer the signalcharge to the vertical transfer area by a CCD readout pulse, and then toapply a transfer signal for producing an output from the CCD 5;alternately repeated after the first drive period is a second driveperiod, in which a drive method is used without application of the CCDreadout pulse (i.e. the CCD readout pulse is OFF) but instead a transfersignal is applied to extract only smear components through the CCD 5from a signal in the vertical transfer area; thereby an AE integrationvalue containing almost no smear component is calculated by using the AEintegration value to record an image in the exposure condition with nosmear effect in actual exposure and image-recording.

Referring to a timing chart of FIG. 2, a description will be given of anoperation of this embodiment.

In this timing chart of FIG. 2, in the same way as the timing chart ofFIG. 5 for a conventional example, each of the horizontal axesrepresents time and is separated into two sections because of limitedspace, the right end of the axis in the upper section continuing to theleft end of the axis that has the same alphabetical letter (i) (i=a, b,. . . , f) in the respective lower section. Other figures such as FIG. 2are displayed in the same way.

In FIGS. 2,(a)–(f) respectively represent a mechanical shutter, CCDreadout pulse ON/OFF, exposure time, CCD output, AE area integration,and AE operation.

The mechanical shutter (mecha-shutter) shown in FIG. 2( a) is kept OPENuntil it receives a shutter trigger, and it changes to the CLOSE stateupon receipt of a shutter trigger.

As shown in FIG. 2-(b), the CCD readout pulse transferring from thephotosensitive area (photoelectric conversion area) of the CCD 5 to thetransfer area is switched from an ON state to an OFF state after asignal charge exposed by a common drive method at the exposure time TI(I=1, 2, . . . , n) shown in FIG. 2-(c) has been output; and in this OFFstate, a signal in the horizontal transfer area is output from the CCD 5by a transfer signal.

In particular, in the image-capture period corresponding to one imageplane, after the exposure time TI, a signal charge of the photoelectricconversion area is transferred by a CCD readout pulse to the verticaltransfer area of the photosensitive conversion area, and, throughapplication of a transfer signal, the transferred signal charge in thevertical transfer area is serially output from the CCD 5. This output isindicated as the (d) item of CCD output in FIG. 2.

The CCD output is input not only to the signal conditioning circuit 10but also to the integration circuit 13 through the S/H circuit 7, the GCcircuit 8, and A/D converter 9. This integration circuit 13 iscontrolled by the exposure operation/control circuit 14 to performintegrating operations during the time when the CCD output in the AEarea is being input, and after having performed an integrating operationin the AE area, it then outputs the AE area integration value EI+SIshown in FIG. 2-(e) to the exposure operation/control circuit 14.

In this value, EI represents a net integration value of the signalcharge accumulated in the photoelectric conversion area (AE sensingarea) at the exposure time TI; SI represents an integration value of aso-called smear occurring in the vertical transfer area because ofoblique incidence transmission of a bright subject image and the like.

Consecutive to the above, the CCD readout pulse is turned to OFF andnull signal charge is output from the CCD 5 through application of atransfer signal (in the same way as for the signal charge which is notnull). In this case, since exposure time is not applied, it is virtuallyindicated by X and a dot line in FIG. 2-(c).

For this CCD output as well, the integration circuit 13 performs theintegrating operation with the timing where the CCD output is beinginput from the AE area and then outputs the AE area integration valueSI′ to the exposure operation/control circuit 14.

This AE area integration value SI′ is almost the same as the AE areaintegration value SI produced with the previous timing, except when animage subject is suddenly moved (against the camera 1). The value inthis case is therefore SI≈SI′, which shows the two are nearly the same.

The exposure operation/control circuit 14 performs the AE operation fromthe two AE area integration values EI+SI and SI′. In particular, thiscircuit performs the operation to determine whether the operationEI+SI−SI′ is larger than the target value; if EI+SI−SI′>target value,the circuit then sets TI>TI+1 to the next exposure time TI+1; ifEI+SI−SI′<target value, the circuit then sets TI<TI+1 to the nextexposure time TI+1.

This circuit also conditions the diaphragm 4 and a gain of the GCcircuit 8. When the circuit conditions these, it sets factors inconsideration of the conditioning effects to the exposure time TI+1.

The operation value EI+SI−SI′ thus produced in each of the image-captureperiods results in the value EI containing almost no smear component.

For reference, when the AE area integration value EI+SI or SI′ isreceived, the aperture of the diaphragm 4 and the gain of the GC circuit8 are maintained at the same value.

These operations are repeated in series for each of the image-captureperiods. However, when the release switch is operated and an actualshutter trigger for image-recording is received, the exposureoperation/control circuit 14 determines an actual exposure conditionbased on the last AE operation value En+Sn−Sn′≈(−En), controls the TGcircuit 6 to operate at the actual exposure time in the actualcondition, and then sets the aperture of the diaphragm 4.

Consecutive to the above, the signal charge accumulated in thephotoelectric conversion area during the actual exposure time istransferred to the vertical transfer area by the CCD readout pulse whichhas been turned to ON, and concurrently, the mechanical shutter 3 isshut off. In the state where the mechanical shutter 3 is kept closed,the signal charge transferred to the vertical transfer area isvertically transferred by the transfer signal and the signal chargewhich has been transferred to the horizontal transfer area is seriallyoutput from an output terminal thereof, is signal-conditioned in thesignal conditioning circuit 10, is compressed by an image compressioncircuit (such as a JPEG circuit) of the record system 11, and is storedin a record medium, such as a memory card and the like.

The mechanical shutter 3 is at least kept closed during the CCD outputperiod (specifically, the vertical transfer period); thereafter, itopens.

Upon completion of the record operation in the record system 11, itbecomes ready to start a subsequent still-image capturing operation.

According to the embodiment in which the operations are performed asdescribed above, because an AE operation value containing almost nosmear component can be produced, when an image is actually recorded andeven after the mechanical shutter 3 is closed, smear-induced deviationsin the exposure amount from a proper exposure amount can be almostcompletely prevented. Consequently, even in a bright image subjectscene, image record operations can be performed in a proper exposurecondition containing almost no smear effect.

Next, a description will be given of a second embodiment of the presentinvention with reference to a timing chart of FIG. 3. This embodiment isrelevant to FIG. 1 in construction, but is different in the operation.

Particularly, this embodiment performs the operation in almost the samemanner as the conventional example such as that shown in FIG. 5 until itreceives a shutter trigger. Upon receipt of a shutter trigger, however,in this embodiment a CCD readout pulse is set to an OFF state and beginsto read null signal charge in a vertical transfer area (i.e. so-calledsmear-component extraction), and after performing an AE operationcontaining almost no smear component as in the first embodiment, itdetermines an actual exposure condition to perform the image-recording.

The timing chart of FIG. 3 is illustrative of the same performance asthe conventional example during the time before a shutter trigger isreceived. In this performance, the CCD readout pulse is kept in an ONstate until a shutter trigger is received, a signal charge in thephotoelectric conversion area of the CCD 5 is transferred to thevertical transfer area after the exposure time TI, and then the signalcharge transferred in the vertical transfer area has vertical andhorizontal transfer signals applied thereto, and thus a CCD output isproduced.

A signal corresponding to the AE sensing area in this CCD output step issubjected to an integrating operation in the integration circuit 13 andthe integration value EI+SI is input to the exposure operation/controlcircuit 14.

The exposure operation/control circuit 14 then performs an AE operationfor automatic exposure and a comparison operation to compare theintegration value EI+SI to a target value. If the EI+SI>target value,the circuit 14 determines the next exposure time TI+1 so as to beTI>TI+1; while, if the EI+SI<target value, it determines the nextexposure time TI+1 so as to be TI<TI+1.

In this way, when the next exposure time TI+1 is consecutivelydetermined and a release operation is performed after the exposure timeTn, this embodiment is then arranged to operate similar to the firstembodiment.

Upon receipt of a shutter trigger, a CCD output that contained the smearcomponent during the last exposure time Tn is output, the CCD readoutpulse is set to be in an OFF state, and then null signal charge in thevertical transfer area is transferred to be output from the CCD 5; afterall, only the smear component is output.

The exposure operation/control circuit 14 uses the CCD output of theintegration circuit 13, which contained the smear component during theaforementioned exposure time Tn, to receive an integration value Sn′containing only the smear component in the same case as the integrationvalue En+Sn.

The exposure operation/control circuit 14 then receives an AE operationvalue En+Sn−Sn′ from the integration values En+Sn and Sn′, based onwhich it determines an actual exposure condition.

In actual image-recording with this embodiment, the target value or areference exposure condition is determined from the last AE operationvalue En+Sn−Sn′, i.e. the AE operation value En containing almost nosmear component, so that an appropriate exposure condition isdetermined.

Accordingly, this allows actual image-recording in appropriateconditions despite that when a shutter trigger is not received, theexposure condition includes an AE area integration value which is largerto correspond to the smear component, causing the CCD output darker.

According to this embodiment, control-related operations performed inthe first embodiment can be eliminated because the null-readout forextracting the smear component is not necessary until a shutter triggeris received.

In addition, in the first embodiment, an image cannot be produced duringany of the periods in which the null-readout for the smear-componentextraction is performed, causing the LCD 12 to display images only inthe periods in which the images can actually be produced. In this secondembodiment, however, only one effect such as that described above occurswhen the shutter trigger is received, allowing the display ofsmoothly-moving images on the LCD 12.

Next, a description will be given of a third embodiment of the presentinvention with reference to a timing chart of FIG. 4. This embodiment isrelevant to FIG. 1 in construction in which the CCD readout pulse ON/OFFis always set to be in an ON state, but is different in the operation.

Before receiving a shutter trigger, in this embodiment is performedexposure at two different times and an AE operation value containingalmost no smear component is received from the CCD outputs; and when ashutter trigger is received, in this embodiment, exposure conditions aredetermined from an AE operation value containing almost no smearcomponent; thereby allowing image-recording with almost no smear effectand with an appropriate brightness. In this embodiment, as shown in FIG.4-(c) for example, an image is captured practically at each of thedouble exposure time 2TI and single exposure time TI and, after eachtime has elapsed, an image is output from the CCD 5 in the common CCDdrive method.

Then, as shown in FIG. 4-(e), the integration circuit 13 receives theintegration values 2EI+SI and EI′+SI′ in the AE area with each of theCCD outputs to output the image to the exposure operation/controlcircuit 14.

This exposure operation/control circuit 14 uses the integration values2EI+SI and EI′+SI′ to compare the AE operation value 2EI+SI−(EI′+SI′) toa target value. If 2EI+SI−(EI′+SI′)>target value, the circuit 14 thendetermines the next exposure time TI+1 so as to be TI>TI+1; andconversely, if 2EI+SI−(EI′+SI′)<target value, it then determines thenext exposure time TI+1 so as to be TI<TI+1.

In this case, the smear amount depends upon the substrate-surfaceilluminance and the transfer time in the CCD 5; however, since it doesnot depend upon the exposure time, it is possible to assume it as EI≈EI′and SI≈SI′.

For this reason, the AE operation value 2EI+SI−(EI′+SI′) is allowed toreceive a value EI containing almost no smear component, and based onthis value, the next exposure time and the like are determined.

Also, in the same way as the first embodiment, upon receipt of a shuttertrigger, the AE operation value 2En+Sn−(En′+Sn′) (≈AE operation valueEn) received in the last image-capture period is used for determinationof the actual exposure conditions.

In this embodiment can be performed is image-recording in appropriateexposure conditions without receiving a smear-component effect from theCCD output produced when an image is captured at two different exposuretimes, one being a single exposure time and the other being a doubleexposure time.

For reference, a single exposure time and a double exposure time are setin this embodiment; however, the setting of the exposure times is notlimited thereto. For example, the exposure time may be set at 1.5 timesas much and the value 0.5 EI that can be approximately obtained from anAE operation may be set at twice as much to determine the next exposuretime and the like. In other words, one exposure time TI may be set so asto be at least a different exposure time from another exposure time.

A variation example of this is an arrangement in which the next exposuretime and the like may be determined by setting the two exposure times ineach of the image-capture periods to the same exposure time, changingthe horizontal transfer time to receive a smear-component evaluationvalue, subtracting the evaluation value from an AE operation valuecontaining the smear component to receive an AE operation valuecontaining almost no smear component, and using the AE operation valuethus produced.

According to the present invention such as described above, in anautomatic exposure control apparatus receiving an exposure evaluationvalue from an output signal of a solid-state imaging device and usingthe evaluation value as a reference value to perform automatic exposurecontrol for the solid-state imaging device, because an exposureevaluation value containing almost no smear component from two outputsignals received through application of the same drive signal from thesolid-state imaging device as was image-captured in a first exposuretime and in an exposure time which is practically twice that of thefirst exposure time is received, exposure errors resulting from thesmear component can be eliminated almost completely and appropriateexposure can be automatically obtained even in bright scenes in whichsmears can occur.

1. An automatic exposure control apparatus receiving an exposureevaluation value from an output signal of a solid-state imaging deviceand using the evaluation value as a reference value to perform automaticexposure control for the solid-state imaging device, characterized bycomprising an arrangement configured for receiving an exposureevaluation value containing almost no smear component based on obtaininga difference between first and second signals respectively receivedthrough application of the same drive signal from the solid-stateimaging device that has been image-captured in a first exposure time andin a second exposure time which is practically twice that of said firstexposure time.
 2. The apparatus of claim 1 wherein the second exposuretime is two times a normal exposure time.
 3. The apparatus of claim 1wherein smear components obtained in the first and second exposure timesare substantially equal.
 4. The apparatus of claim 1 wherein the firstsignal has a first charge component and the second signal has a secondcharge component having a value which is twice that of the first chargecomponent.
 5. The apparatus of claim 1 wherein said arrangement directlysubtracts one of said first and second signals from the other one ofsaid first and second signals.
 6. The apparatus of claim 1 furthercomprising a unit for comparing, during each exposure period, theexposure evaluation value with a threshold value and increasing theexposure period, for use during a next exposure period, if the exposureevaluation value is less than said threshold value.
 7. The apparatus ofclaim 1 further comprising a unit for comparing, during each exposureperiod, the exposure evaluation value with a threshold value andreducing the exposure period, for use during a next exposure period, ifthe exposure evaluation value is greater than said threshold value. 8.The apparatus of claim 1 wherein said arrangement obtains the exposureevaluation value by being configured to directly subtract one of thefirst and second signals from the other.
 9. An automatic exposurecontrol apparatus receiving an exposure evaluation value from an outputsignal of a solid-state imaging device and using the evaluation value asa reference value to perform automatic exposure control for thesolid-state imaging device, characterized by comprising an arrangementconfigured for generating an exposure evaluation value containing almostno smear component based on a obtaining difference between first andsecond output signals received through application of the same drivesignal from the solid-state imaging device that has been image-capturedin a first exposure time and in an exposure time which is different fromsaid first exposure time.
 10. The apparatus of claim 9 wherein thesecond exposure time is one-and-one half times a normal exposure time.11. The apparatus of claim 9 wherein the first and second signals havesmear components which are substantially equal.
 12. The apparatus ofclaim 9 further comprising a device for combining the first and secondsignals to remove the smear components.
 13. The apparatus of claim 9further comprising a unit for comparing, during each exposure period,the exposure evaluation value with a threshold value and increasing theexposure period, for use during a next exposure period, if the exposureevaluation value is less than said threshold value.
 14. The apparatus ofclaim 9 further comprising a unit for comparing, during each exposureperiod, the exposure evaluation value with a threshold value andreducing the exposure time, for use during a next exposure period, ifthe exposure evaluation value is greater than said threshold value. 15.The apparatus of claim 9 wherein said arrangement obtains the exposureevaluation value by being configured to directly subtract one of thefirst and second signals from the other.
 16. A method for operating aphotoelectric conversion device to obtain an exposure evaluation value,comprising: a) reading out from the conversion device, during a firstinterval of an exposure period, a first integrated exposure value and asmear value; b) reading out from the conversion device, during a secondinterval of said exposure period, a second integrated exposure value anda smear value, said first and second time intervals being different; andc) employing the values obtained during steps (a) and (b) to obtain saidexposure evaluation value.
 17. The method of claim 16 wherein one ofsaid first and second intervals is twice as great as the other one ofsaid first and second time intervals.
 18. The method of claim 16 furthercomprising: during each exposure period, comparing the exposureevaluation value with a threshold value; and increasing the exposureperiod, for use during a next exposure period, when the exposureevaluation value is less than the threshold value.
 19. The method ofclaim 16 further comprising: during each exposure period, comparing theexposure evaluation value with a threshold value; and reducing theexposure period, for use during a next exposure period, when theexposure evaluation value is less than the threshold value.
 20. Themethod of claim 16 wherein step (c) further comprises subtracting thevalue obtained in one of the steps (a) and (b) from the value obtainedin the other of the steps and (a) and (b).
 21. An automatic exposurecontrol apparatus receiving an exposure evaluation value from an outputsignal of a photoelectric conversion area performing photoelectricconversion and an output signal of a solid-state imaging devicecomprising a transfer area wherein the signal is transferred from thephotoelectric conversion area and using the evaluation value as areference value to perform automatic exposure control for thesolid-state imaging device, characterized by comprising a first driveunit for transferring a first exposure signal and a smear signal in saidphotoelectric conversion area during a first interval in each exposureperiod to a transfer area and then outputting the first exposure signaland smear signal from said solid-state imaging device; and a seconddrive unit for outputting a second exposure signal and a smear signal insaid photoelectric conversion area during a second interval of eachexposure period from solid-state imaging device, the first and secondintervals being different; wherein is obtained an exposure evaluationvalue containing almost no smear component based upon the a differencebetween two output signals received from said first drive unit and saidsecond drive unit.
 22. The apparatus of claim 21 wherein one of saidfirst and second signals is twice as great as the other one of saidfirst and second signals.
 23. The apparatus of claim 21 wherein thedifference is obtained by subtracting one of the output signals of thefirst and second drive units from the other.